The invention relates to a method and a device for automatically determining the concentration of nitrite in a liquid sample.
Such methods and devices are employed, inter alia, in waste water clarification plants for monitoring and controlling the clarifications process. In the known measuring methods and devices, the extinction of the liquid sample of the waste water is determined with the aid of UV radiation. Using the extinction value obtained in this manner, the concentration of the sum of nitrite and nitrate is calculated. Since the spectral curve shapes of the extinction of nitrite and nitrate show large similarities, photometric means virtually do not allow for an exact differentiated determination of nitrite or nitrate in a liquid sample containing both nitrite and nitrate. However, monitoring or controlling the correct process of nitrification, i.e. the microbiological oxidation of ammonium over nitrite using Nitrosomonas, and the subsequent microbiological oxidation of nitrite to nitrate using Nitrobacter, requires individual determination of both the concentration of nitrite and the concentration of nitrate.
It is thus an object of the invention to provide a method and a device for automatically determining the concentration of nitrite in a liquid sample possibly containing nitrate.